The Permanent Portfolio was proposed by Harry Browne in the book Fail Safe Investing.  An excellent modern guide is The Permanent Portfolio: Harry Browne’s Long-Term Investment Strategy by Craig Rowland and J. M. Lawson.

Asset Allocation

• 25% Total Domestic Market
• 25% Long Term Bonds
• 25% Tbills/Cash
• 25% Gold

 

Note: Short Term Bonds are a common substitute for Cash for many Permanent Portfolio investors.